System of control for electric motors.



B LAMME.

SYSTEM OF CONTROL, FOR ELECTRIC MOTORS.

- APPLICATION IILED SEPT.26, 1910. 1 O66,507;

Patented July 8,1913.

ATTOIRNEY BENJAMIN G. LAMME, OF PITTSBURGH, PENNSYIVANIA,

assrcn'on 'ro wnsrmc- HOUSE nnnc'rmc AND MANUFACTURING ooMrAn'Y, A conronnrron' or PENNSYL- VANIA,

Specification 0:! Letters 2atent.

I SYSTEM OF CONTROL FOR ELEGTRIC MOTORS.

Patented July8,1913.

Application filed September 26, 1910.. Serial. No. 583,880.

To all whom. it may concern Be it known that .I, B NJAMIN Gr. LAMME, a citizen of the United States, and a resident of Pittsburgh, in. the county of Allegheny and Stateof Pennsylvania, have invented a new and useful Improvement in Systems of Control for Electric Motors, of which the following is a specification.

My invention relates to systems of control for electric motors and it has special reference to such systems as are adapted to control the starting operation of an induction motor of large capacity and relatively low voltage.

I The objectof my invention is to provide a system of the abovedndicated class that shall be simple in'arran'gement and operation and. especially adapted to reduce the size and expense of the switching apparatus usually employed in connection with the starting of motors of this type.

One of the notable advances in industrial and manufacturing enterprises in recent years has been the general demand and use of larger and more efficient machinery and driving units. In this connection, it been necessary to increase the size and capacity of electrical machinery and apparatus, which has necessarily involved. new operating conditions and difficulties, pre viously not encountered.

The development of polyphase induction motors of large capacities has been particularly marked, and the method of starting such motors has been a matter of considerable importance on account of the increased size and cost of the necessary switching apnections are switched from low voltage taps to higher voltage taps or to the line voltage,

after the motor is started. Sometimes, there 1s but a slngle step from the starting taps to the full-voltage running position, while,

in other cases, there are several intermediate steps, thus giving a more gradual increase in voltage. In general, this tvpe of autostarter is satisfactory, but, for motors of large capacities, it is inadequate, as the switches which transfer the motor connections from lower to higher taps are required to handle the excessive starting motor cur-x rent, which is always much greater than the line current. For instance, if the motor is started at half voltage, the current the motor leads is practically twice that ofthe.

supply circuit. In general, it may be said.

that the motor current has -a ratio to the line current which is inversely proportional to the ratio of the motor and line voltages, at start. Y

.The' difficulty encountered with the usual type of auto-starters for meters of large size andrelatively low voltages, residesin the excessive motor current to be switched. A heavy current is d-iiiicultand costly to handle, on account of the size and constructi'on ofthe necessary switching apparatus, "and it is to reduce this difficulty that my present system of control isintended.-

According to my present invention, a plurality of auto-transformers are provided with taps, as in the usual arrangement, but, instea-d'of switching the motor from one set of taps to another, the line connections'are shifted in a similar manner. Hence, the

switching apparatus is'relieved of its usual,

severe operating conditions. The lowest voltageon the motor is obtained when the supply circuit is connected to the highest tapon the auto-transformers, and increases in motor voltage are secured by graduallyshifting the line connections to lower taps. lt is: the line current, therefore, which is lswitched, instead of the motor current, and, in consequence, the current to be handledi by the switching apparatus is smaller than Zi-n the usual arrangement.

are used on the auto transformers, it is usui ally the first taps which handle the heaviest current and the last taps which handle the least, by reason of the fact that the motor lf several taps has gradually approached synchronism and the current has consequently been reduced- *ly invention can better be understood by reference to the accompanying drawings, in

1 whichtion. Fig. 3 is a table showing the switches of Fig. 2 which are finally closed in each position of the master controller.

Referring to Fig. 1, an auto-transformer 1 having a plurality of taps 2, 3 and 4 and a similar transformer 5 having a plurality of taps 6, 7 and 8 are V-connected at 9, according to well known practice. A threephase induction motor 10 is permanently connected to taps 4, 8 and 9, through conductors 11, 12 and 13, respectively, and a conductor 14, of a three-phase supply circuit .14, 15 and 16, is also permanently connected between the transformer units 1 and 5 at point 9. Conductors 15 and 16 are respectively provided with suitable switching devices 17 and 18, by means of which said conductors may be connected to the various taps 2, 3, 4 and 6, 7, 8, respectively, as desired.

As shown, the supply circuit conductors 15 and 16 are connected to taps 2 and 6, respectively, and hence, it is evident that the lowest voltage is impressed upon the motor 10 for purpose of starting. After the motor 10 is started, the supply circuit connections may be advanced simultaneously to taps 3 and 7, through the a ency of the switching devices 17 and 18, t ereby increasing the voltage supplied to the 'motor 10.

The final step in the starting operation is to simultaneously shift the supply circuit connections of the conductors 15 and 16 to taps 4 and 8, respectively, through-the motor 10 is connected directly to the supply circuit and full line voltage.

It will be observed that all of the switching is accomplished on the supply circuit conductors and hence the diificulties encountered in handling the heavy m'otor currents are obviated and smaller and less expensive switching apparatus may be employed. If a greater number of intermediate volt age steps is desired, the switching devices 17 and 18 may be shifted alternately, in a manner similar to that hereinbefore described, whereby an increased number of more gradually graded steps is obtained.

Reference may now be had to Fig. 2, in which the system of control shown, comrises a sub-divided auto-transformer 1 havmg a plurality of taps 2, 3 and 4 and a similar auto-transformer 5 having a plurality of taps 6, 7 and 8; a polyphase induction motor 10 permanently connected to taps 4 and 8 of the auto-transformers 1 and 5 and adapted to receive energy therefrom; a three-phase supply circuit 14, 1.5 and 16; a plurality of switches 20 and 21 for inter-connecting the autotransformers 1 and 5, according to the usual system of V-connections; a set ofswitches 22 to 29 for adjusting the supply circuit connections to the various taps on the autotransformers 1 and 5; a set of switches 30 to 32 for governing the main supply circuit connections; a plurality of operating electro-magnets 33 to for actuating the switches 20 to 32; a plurality of auxiliary switches 46 to 51 for interlocking the control circuits in order to constrain the operation of the switches 20 to 32 to a predetermined sequence; a plurality of choke-coils 52 and 53 to prevent injurious arcing on the switches 20 to 29; a master controller 54 for governing the control circuit connections of the operating electro-magnets 33 to 45, and comprising a plurality of stationary contact terminals 55 to 59 and a conducting segment 60 which is adapted to coiiperate with said stationary contact terminals upon the position-indicating lines a, b, 0, (Z, e, f, and a battery or other suitable source of energy 61 for supplying energy to the electromagnets 33 to 45.

Assuming the induction motor 10 to be at rest and the various connections to be as shown in Fig. 2, the operation of the system is' as follows: If the conducting seg-' ment 60 is moved into contact with the stationary contact terminals 55 and 56, upon the po-sition indicating line a, a circuit is completed from the positive side of the bat tery 61, through stationary contact terminal 55, conducting segment ,60, stationary contact terminal 56 and conductor 62, where the circuit divides, one branch including conductor 63, electro-magnet 36, conductor 64 and a conductor 65 to the negative side of the battery, and the other branch including conductor 66, electro-magnet 41, conductor 67 and conductor 65, to the negative side of the battery. Uponthe completion of these circuits, the electromagnets 36 and 41 are energized and switches 23 and 28 are closed. As the switch 23 is closed, the auxiliary switch 47 engages the contact terminals 68 and a circuit is thus completed from the conductor 63, through switch 47, conductor 68, conductor 69, conductor 69, switch 49 and conductor 70, where the circuit divides, one branch including conductor 71, 'electro-magnet 33, conductor 72,

. conductor 73 and conductor 65, to the negative side of the battery, and the other branch traversing conductor 74, conductor 75, electro-magnet 34, conductor 76, conductor 73 and conductor 65, to the negative side of the battery. Having established the circuits just recited, the electromagnets 33 and 34 are energized, and switches 20 and 21 are closed. As the closure of the switch 21 is effected, auxiliary switch 50 engages the stationary contact terminals 77, and a circuit is completed from the'conductor 74, through switch 50,, conductor 78 and conductor 79, where the circuit divides, one path traversing conductor 80, electro-magnet 43, conductor 81, conductor 82 and con- I very; a second path includirfg conductor 83,

i i and 5, through switch 31 and conductor 90; 29'

conductor 84, electromagnet 44, conductor 85, conductor 82 and conductor 65 to the negative side of the battery; and a third branch including conductor 83, electromagnet '45, conductor 82 and conductor 65, to the negative side of the battery. Thus, the electaro-magnets 43, 44 and 45 are energized, and

the closure of the switches 30, 31 and 32 is efiected. Upon the closure of switches 30, Z 31 and 32, the supply circuit conductor 15 is connected to tap 2 of the. auto-trans-z former 1, through switch 30, conductor 86, f

' 58 is engaged and electro-niagnets 35 and 42 are caused to close the switches 22 and 29,

a portion of the choke coil 52, conductor '87,

switch 23 and conductor 88; the supply circuit conductor 14 is connected to the V- connection 89 of the auto-transformers 1 and thesupply circuit conductor 16 is connected to tapfi of the auto-transformer 5,

through switgh 32, conductor 91, a portion of the choke coil 53, conductor 92, switch 28,,

and conductor 93. It will be observed that the supply-conductors 15 and 16 are connectcd to the full-voltage taps 2 and 6 of the autotransformers 1 and 5, respectively, and hence, the lowest voltage is applied to the motor 10 for starting. As the conducting segment 60 is moved step-by-step into engagement with the stationary contact terminals 57, 58 and 59, along the position-indicating lines I), a, (Z, c and f, the connections of the supply circuit conductors 15 and 16 to the auto-transformers 1 and 5 are gradually shifted until the motor 10 is finally connected directly to the supply circuit.

On account of the simplicity and simi- 'larity of the control circuits to those hereinhefore described in detail, it is not considerednecessaryto trace each circuit which A brief outline only of the mode of operation will be given, and it is believed that those skilled in the art will experience no difficulty in understanding the same .and in tracing the control circuits therefor.

As the conducting segment 60 is moved into engagement with the stationary contact terminal 57, along the position-indicating line Z), the electromagnets 37 and 40 are energized and the switches 24 and 27 are closed, thus connecting the supply conductors 15 and 16 to the auto-transformer taps 3 and 7, respectively. As the switch 24 is closed, the auxiliary-switch 48 engages the upper contact terminals 94, and thus energy is also supplied to the electromagnets 33, 34, and 43, 44 and 45, through a circuit which includes stationary contact terminal 57, switch 51, switch 48 and switch 49. \Vhen the conducting segment is moved into position a, the engagement with the stationary contact terminal 56 is discontinued thusestablishing supply circuit connections to taps 4 and 8 of the auto-transforme'rsl and 5, respectively. As the switch 22 is closed, another energizing circuit for the electromagnets 33 and-34 is established by way of stationary contact terminal a 58, switch 46 andswitch 49. The disengagement of conducting segment 60 and the stationary contactt'erminal 57 is effected in positione, and switches 24 and 27 are opened, thereby interrupting the supp'ly'circuit connections to the transformer. taps 3 and 7. As the switch 24 is opened, the energizing circuit for the electromagnets 33 and 34, which includes stationary contactterminal 57 switch 51, switch 48 and switch 49, is interrupted, and the-auxiliary switch 48 is caused to engage its lower contact terminals 96. v

I11 the last operating position, f, the stationary contact terminal 59 is engaged, and

electr'o-magnets 38 and 39 become energized and cause switches 25 and 26' to be closed, thus connecting the supply. circuit conductors 15 and 16 directly to the transformer taps 4 and 8, respectively, and impressing full line voltage upon the motor 10. Upon the closure of switch 25, the auxiliary switch 49 disengages the lower contact terminals 97 and therebyinterrupts the energizingcircuit for the electro-magnets 33, 34 and 43, 44 and 45. Hence, switches 20 and 21 are allowed to open and the auto-transformers 1 and 5 are disconnected However, concurrently with the disengagcment of switch 49 from the lower contact terminals 97, its engagement with the upper contact terminal 98 is effected, and an energizing circuit for the electro-magnets 43, 44 and 45 is instantly established and includes stationary contact terminal 59, .switch 49 and switch 48. Hence, energy is supplied to the electromagnets 43, 44 and 45 before said magnets become deenergized on account of the opening of switches 20 and 21, and, therefore, the line switches 30, 31 and 32ers maintained closed. It will also be observed that, in position f, the stationary contact terminal 58 is disengaged and the switches 22 and 29.

are allowed to open, thus interrupting the supply circuit connections to the transformer taps 4 and 8 by Way of the choke coils 52 and 53, respectively; and leaving the supply circuits 15 and 16 connected directly to the motor 10. Full line voltage is thus applied to the motor and full running conditions are established.

As in Fig. 1, it will be observed that, all

of the voltage adjustments are confined to the supply circuit conductors, so that the switching apparatus is not required to handle the excessive motor currents and may,

therefore, be materially reduced in size and expense.

Those skilled in the art will readilyun:

derstand that my invention is. not restricted to the use of auto-transformers or to the specific circuit connections and'arrangements 'herelnbefore shown and described. Obvi-i ously, various othenarrangementsifor two.- phase and three-phase operation may beeffected Without departing from thespirit of my invention, and I desire that all such modifications shall be included 'within it's scope.

Iclaim as my invention: 1. In a system of control, the combination with a plurality of transforming devices, a supply circuit, and an electric motor Dermanently connected to said transforming devices, of means for shifting theconnec- 'tions of said supply-circuit to said trans forming devices and a single device for controlling -the 1 operation 0f said sh fting means. y

"2. In a system of control, the combination with a plurality of transformers, a supsaid motor to said supplycircuit. I 4. In a system of control, the ,combinaply circuit, and an electric motor permanentlyconnected to said transformers, of

' means for shifting said supply circuit connections to symmetrically located interme diate taps on said transformers, including those to which the motor is connected and thereby increasing the voltage applied to said motor and connecting said supply circuit directly thereto.

I 3. In a system of control, the Combina tion with a plurality of transformers, a.

supply circuit connected thereto, and an electric motor permanently connected to intermediate taps on said transformers, of means dependent upon shifting the supply circuit connections to said transformers for gradually increasing the initial voltage applied to said motor and finally tion with a plurality of interconnected transformers, each provided ith-a plurality or" symmetrically located intermediate taps, a supply circuit initially connected to, the full-voltage taps of said transformers, and an electric motor permanently connected to symmetrically located intermediate taps, of

is gradually raised to line voltage.

termediate taps of said auto-starter, of a connecting means for gradually shifting said supply circuit connections step by step to said intermediate taps to which said motor is connected. V

5. In a system of control, the combination with an auto-starter having different voltage taps, a supply circuit adapted to be connectedthereto, and an induction motor permanently connected to certain of said taps, of means for successively shifting the supply circuit connections to said auto-starter .taps and finally connecting said supply circuit to the taps to which said motor is connected, whereby the Voltage on said motor 6. In a system of control, the comblnatlon .With an auto-starter, a supply circuit adapted to be connected thereto, and an induction motor permanently connected to certain inlurality of switches, and a single means or controlling the operation thereof, whereby the 'supply circuit connections to saidv auto-starter are shifted, for the purpose of starting the motor. i

Y '90 7. In "a system of control, the combination with a plurality of V-connected autotransformers, a supply circuit, and an electric motor permanently connected to certain intermediate taps of said auto-transv formers, of switches for successively con necting the supply circuit to difi'erent voltage taps, including the motor taps, and a single device for controlling said switches.

8. In a system of control, the combination with an auto-starter, a supply circuit initially connected to the full-voltage tapsthereof, and an induction motor perma 'nently connected to intermediate taps on. said auto-starter for the purpose of starting 5 said motor, of means for gradually shifting said supply circuit connect-ions to the taps to which said motor is permanently connected. I I '9. In a control system,the-combination with afplurality of transformers, a supply circuit,ia'n electric motor connected to intermediate taps; on said transformers, and a plurality of choke coils, of a plurality of electrically operated switchesand means for cjmtrollingthe operation thereof, whereby transformers areinterconnected, said supply circuit is connected through said permanently connected to said intermediate taps, a pluralit of choke coils and a plurality of electrically operated switches, of means for controlling the operation of said switches, whereby said auto-transformers are interconnected, said supply circuit is connected to said auto-transformers through said choke coils, said supply circuit connections are shifted step by step to said intermediate taps to which said motor is connected, said choke coils being in circuit, said choke coils are eliminated from the circuit and said auto-transformers are disconnected, leaving said motor connected directly to said supply circuit.

11. In a control system, the combination with a plurality of transformers, a supply circuit connected thereto, and an electric 6. motor permanently connected to intermediate taps in said transformers, of aplurality of electro-responsive devices for efl'ecting changes in the supply circuit connections Copies of this patent may be obtained for and single means for controlling the energization of said elect-ro-responsive devices.

12. In a system of control, the combination with an auto-starter having a plurality of difi'erent voltage taps, a supply circult adapted to be connected thereto, and a motor permanently connected to certain of said taps, of a plurality of electromagnetically operated switches associated with the different voltage taps, and a master controller for effecting the operation of said switches in a predetermined sequence whereby said supply circuit connections are successively shifted to the taps to which said motor is connected.

In testimony whereof, I have hereunto" subscribed my name this th day of Sept,

five cents each, by addressing the Commissioner of Patents, Washington, I). G. a 

